<b>Grading Acanthosis Nigricans Using a Smartphone and Color Analysis: A Novel Noninvasive Method to Screen for Impaired Glucose Tolerance and Type 2 Diabetes</b>

Abstract

<p dir="ltr">Objective. The objective of this study was to develop ANcam, a novel method for identifying acanthosis nigricans (AN) using a smartphone camera and computer-aided color analysis for noninvasive screening of people with impaired glucose tolerance (IGT). Research Design and Methods. Adult and juvenile participants with or without diagnosed type 2 diabetes were recruited in Trinidad and Tobago. After obtaining informed consent, participants’ history, demographics, anthropometrics, and A1C were collected and recorded. Three subject-matter experts independently graded pictures of the posterior neck and upper back using the ANcam smartphone application and Burke methods. A correlation matrix investigated 25 color channels for association with hyperpigmentation, and the diagnostic thresholds were determined with a receiver operating characteristic curve analysis. Results. For the 227 participants with captured images and A1C values, the cyan/magenta/yellow/black (CMYK) model color channel CMYK_K was best correlated with IGT at an A1C cut-off of 5.7% [39 mmol/mol] (R = 0.45, P <0.001). With high predictive accuracy (area under the curve = 0.854), the cut-off of 7.67 CMYK_K units was chosen, with a sensitivity of 81.1% and a specificity of 70.3%. ANcam had low inter-rater variance (F = 1.99, P = 0.137) compared to Burke grading (F = 105.71, P <0.001). ANcam detected hyperpigmentation on the neck at double the self-reported frequency. Elevated BMI was 2.9 (95% CI 1.9–4.3) times more likely, elevated blood pressure was 1.7 (95% CI 1.2–2.4) times more likely, and greater waist-to-hip ratio was 2.3 (95% CI 1.4–3.6) times more likely with AN present. Conclusion. ANcam offers a sensitive, reproducible, and user-friendly IGT screening tool to any smartphone user that performs well with most skin tones and lighting conditions. Key Points · A computer-aided screening tool for acanthosis nigricans (AN) quantifies hyperpigmentation and directs users to medical interventions. · Using a smartphone image, hyperpigmentation can be detected and associations with impaired glucose tolerance (IGT) can be made. · Of 25 color channels investigated, the cyan/magenta/yellow/black (CMYK) model CMYK_K channel was found to be best correlated with IGT. ANcam had high predictive accuracy, with both high sensitivity (81.1%), and high specificity (70.3%), detecting AN twice as many times as self-observation. · ANcam is a user-friendly tool that can be used with any skin tone and most lighting conditions, even by laypersons, to detect AN and screen for type 2 diabetes.</p>